Chemistry 1027A/B Chapter Notes -Molar Mass, Chemical Formula, Atomic Number
Document Summary
Electrons- -ve proton n neutrons-found in nucleus of atom. Electrons small n light-1/200th of mass of a proton or neutron. All atoms of the same element have same # of protons in the nucleus ex-6 protons=c. Mass number mass #= total # protons +# neutrons in an atom. Another notation chemical symbol followed by mass number ex- na-23. Same # of protons but different # of neutrons=isotope. Some elements have more then 1 isotope and there can be more then 1 isotope than another ( 1 isotope can be more commonly found then another) Isotopic abundance is the % by # of each of the isotopes of an element. Average atomic mass= percent isotopic abundance/100 x isotopic. Atomic mass standard is based on the mass of c-12. Atomic masses of all other elements in the periodic table have been measured using c- 1 amu is define as exactly 1/12 the mass of c-12.